Influence of Impurities from Manufacturing Process on the Toxicity Profile of Boron Nitride Nanotubes

The toxicity of boron nitride nanotubes (BNNTs) is confounded by the various manufacturing and purification strategies employed targeted to remove 30-60% of the residuals and impurities. Four BNNTs manufactured by the induction thermal plasma process allowed us to assess the influence of these residuals/impurities on the toxicity profile of BNNTs by producing a gradient of BNNT purity levels through sequential gas purification, and water and solvent washing, followed by filtration. Extensive characterization including Infrared, x-ray spectroscopy, thermogravimetric analysis, size, charge, surface area and density allowed characterization of the alteration in physicochemical properties as the material went through sequential purification. The material from each step was screened using acellular and in vitro assays that evaluated general toxicity, mechanisms of toxicity and macrophage function.